This invention relates to a retractable type lens barrel for photographic lenses provided on cameras.
For portability, a camera has conventionally been made thinner by narrowing the distance between lens groups which are optical elements constituting its photographic optical system, and storing in the camera when the camera is not used. Generally, such a camera adopting so-called a retractable lens barrel comes into wide use.
A general retractable type lens barrel is composed of a stationary barrel having a cam groove on the inner circumferential surface thereof, a cam barrel having a cam pin which is engaged with the cam groove of the stationary barrel on the outer circumferential surface thereof and a cam groove on the inner circumferential surface thereof and supported to rotate and move along the optical axis, and a lens retainer having a cam pin which is engaged with the cam groove of the cam barrel, wherein the cam barrel relatively moves the lens retainer along the optical axis for zooming and retracting when rotated.
For example, there has been disclosed a lens barrel having a cam groove for retracting and a cam groove for picture-taking on the stationary barrel, wherein the cam groove for retracting is shallower than the cam groove for picture-taking. (See Patent Document 1.)
[Patent Document 1] Japanese Non-Examined Patent Publication 2003-43336
The lens barrel as described in Patent Document 1 provides, on the stationary barrel, a notched part to have a driving gear mechanism to rotate the cam barrel and a straight guide groove with which a straight guide is engaged. Generally, the notched part and the straight guide groove are provided away from the cam grooves.
However, under some conditions, the notched part or the straight guide groove must be provided across the cam groove which is formed on the stationary barrel.
For example, the notched part at which a driving gear mechanism is arranged or the straight guide groove with which a straight guide is engaged, must be provided across the cam groove on the stationary barrel when the cam groove extends circumferentially at a gradual inclination while the cam barrel is moved forward instead of the configuration in which the cam barrel is singly moved from the retracted position to the front-most position and rotated there for zooming.
Further, straight guide grooves must be provided across part of cam grooves on the stationary barrel also when multiple straight guides, for example four guide grooves away from diagonal lines of a screen, are provided to move the straight guide smoothly along the straight guide grooves in addition to the notched part which has a driving gear mechanism.
When the notched part or the straight guide groove is provided across part of a cam groove, it may sometimes happen that the cam pin goes out of the cam groove at the intersection of the cam groove and the notched part or the straight guide groove and that the cam pin or groove may be partially worn out. In extreme cases, the barrel may be disabled to move.